Composite shafts are typically made in tubular form and are comprised of fiber reinforced plastic material. The fibers can be any number of fibrous materials, including glass and synthetic polymers. The reinforcing fibers are wound around the tubular composite, and are typically arranged such that they intersect each other at various angles.
Composite shafts have been used in a variety of applications, including vehicle drive shafts. U.S. Pat. No. 4,041,599 to Smith illustrates such an application of a composite shaft and is herein incorporated by reference in its entirety.
Due to their composite nature and structure, composite shafts offer several advantages over metal shafts. For example, composite shafts are significantly lighter in weight than metal shafts, thereby making them easy to transport and manipulate during subsequent manufacturing. Also, their light weight reduces their contribution to the overall weight of the article into which they are incorporated, such as a motor vehicle. Furthermore, composite shafts are more resistant to corrosion and other damaging processes than metal shafts. Lastly, primarily due to the arrangement of the fibers in the shaft, composite shafts have high strength and are able to withstand high degrees of stress.
Due to the use of fibrous materials, it can prove difficult to create a joint between a composite shaft and a metal member, such as a hub. Direct weld joints between composite shafts and metal do not normally create strong and durable connections on a consistent and reliable basis. Many approaches to overcoming this disadvantage have been proposed. For example, the use of metallic sleeves to provide a metal surface onto which weld joints can be formed has been proposed. Furthermore, many techniques for securing such sleeves to composite shafts have been explored. U.S. Pat. No. 4,265,951 to Yates et al. discloses the integral formation of metallic connector sleeves in the composite shaft. Another method of securing the sleeves to the shaft employs an adhesive. For example, U.S. Pat. No. 4,722,717 to Salzman et al. discloses a series of grooves on the metallic insert and the composite shaft. When aligned, the grooves form keyways into which adhesive material can be injected. Once polymerized, the adhesive forms a bond between the metallic insert and the composite shaft. Lastly, temperature dependent methods of securing a metallic sleeve to a composite shaft have been proposed. For example, a frozen metallic sleeve can be inserted into a composite shaft and subsequently warmed to expand the metal. In its expanded state, the sleeve is in compression against the shaft.
These various approaches to securing metallic sleeves to composite shafts, although effective, include several disadvantages. For example, integral formation of sleeves onto a shaft requires attachment of the sleeve at the time of manufacturing the shaft. This requirement may inhibit the manufacturing process and furthermore may inhibit other uses of the composite shaft. The use of adhesives requires delicate manufacturing techniques. Lastly, temperature dependent methods require precise control over manufacturing conditions and the manufacturing environment, adding time and expense to the manufacturing process.
Due to the significant advantages offered by composite shafts, demand for these shafts is currently increasing for a variety of applications, including automobile driveshafts. Therefore, there is a need for an assembly that provides a stable surface onto which weld joints can be formed without adding any additional disadvantages, such as burdensome complications to the fabrication process. Furthermore, there is a need for a method of producing such an assembly.